Accessory circuits for operation of a fluorescent lamp, and particularly for low-power, single-ended fluorescent lamps, are well known, and the referenced publication "Elektronikschaltungen" ("Electronic Circuits") by Walter Hirschmann, published by SIEMENS AG, 1982, particularly pages 147 and 148, describes a circuit having a pair of transistors, the bases of which are connected to a control circuit which includes an inductive impedance and, if necessary, an ohmic series resistor. The two inductive impedances each have one winding and are located on a common transformer core.
The transformer core, typically, is a toroidal core or ring-shaped core which is tiny. It operates as a saturating transformer, and has an outer diameter of only about 12 mm; the inner diameter of the core is only about 5 mm.
It has been found that it is particularly difficult to apply one or more windings to such a core, particularly under mass production conditions. The tiny core dimensions make it difficult to apply windings thereon. It is rather difficult to apply one winding over a portion of the circumference of the core; adding a further winding, and particularly adding further windings beyond the first one, is extremely difficult and time-consuming.